# The following reaction is known to occur in the body. If $CO_2$ escapes from the system : <br> $CO_2 + H_2O \leftrightharpoons H_2CO_3 \leftrightharpoons H^+ + HCO_3^-$
( A ) $H^+$ ion concentration decreases
( B ) $H_2CO_3$ concentration does not change
( D ) $H^+$ ion concentration increases